What is a normal FSH level by age?

In reproductive-age women FSH is roughly 3.5-12.5 mIU/mL in the follicular phase, with a mid-cycle surge up to about 21 mIU/mL. After menopause it rises to a representative range of about 25.8-134.8 mIU/mL. Ranges vary by laboratory.

What FSH level confirms menopause?

No single number confirms menopause. A sustained FSH above about 30 mIU/mL alongside 12 consecutive months without a period supports the diagnosis, but perimenopausal FSH fluctuates, so clinicians weigh symptoms and cycle history rather than one test.

Can FSH be high one month and normal the next?

Yes. During perimenopause FSH commonly swings between near-normal and clearly elevated from cycle to cycle. This day-to-day variability is exactly why a single FSH draw is unreliable for diagnosing the menopausal transition.

What does a low FSH level mean?

Low FSH, especially with low estradiol, suggests the signal from the hypothalamus or pituitary is reduced — seen in hypothalamic amenorrhea (from stress, low body weight, or overtraining) or pituitary conditions. A clinician evaluates the cause.

What is a normal FSH level by age?

In reproductive-age women FSH is roughly 3.5-12.5 mIU/mL in the follicular phase, with a mid-cycle surge up to about 21 mIU/mL. After menopause it rises to a representative range of about 25.8-134.8 mIU/mL. Ranges vary by laboratory.

No single number confirms menopause. A sustained FSH above about 30 mIU/mL alongside 12 consecutive months without a period supports the diagnosis, but perimenopausal FSH fluctuates, so clinicians weigh symptoms and cycle history rather than one test.

Yes. During perimenopause FSH commonly swings between near-normal and clearly elevated from cycle to cycle. This day-to-day variability is exactly why a single FSH draw is unreliable for diagnosing the menopausal transition.

Low FSH, especially with low estradiol, suggests the signal from the hypothalamus or pituitary is reduced — seen in hypothalamic amenorrhea (from stress, low body weight, or overtraining) or pituitary conditions. A clinician evaluates the cause.

Reference-range chart

Normal FSH levels by age (reference range chart)

Follicle-stimulating hormone (FSH) is low before puberty, cycles through the reproductive years (roughly 3.5-12.5 mIU/mL in the follicular phase with a mid-cycle surge), and rises sharply after menopause to about 25-135 mIU/mL. A sustained FSH above 30 mIU/mL with absent periods supports menopause, but perimenopausal FSH fluctuates too much to confirm it on one draw.

FSH reference ranges by age

Representative FSH reference ranges by life stage and cycle phase. Representative intervals only — values vary by laboratory and assay.
Life stage / cycle phase	FSH (mIU/mL)	Notes
Before puberty	0-4	Low before puberty
Reproductive — follicular phase	3.5-12.5	Baseline of the cycle
Reproductive — mid-cycle (ovulatory) peak	4.7-21.5	Surge that triggers ovulation
Reproductive — luteal phase	1.7-7.7	Falls after ovulation
Perimenopause	Variable (often > 10-25, with swings)	Rises but fluctuates — one draw cannot confirm menopause
Postmenopausal	25.8-134.8	Sustained elevation as ovarian reserve is exhausted

How fsh is measured

FSH is measured from a blood sample, ideally on cycle days 2-5 when a woman is still menstruating. The values below are representative (Mayo Clinic Laboratories); mIU/mL and IU/L are numerically equivalent. Because perimenopausal FSH swings from day to day, clinicians rarely rely on a single value. Interpret results with your ordering clinician.

How to read your result

FSH rises as the ovaries run out of responsive follicles, which is why it climbs through the menopausal transition.
A sustained FSH above 30 mIU/mL together with 12 months of no periods is consistent with menopause; a single high value in a still-cycling woman is not diagnostic.
In a woman under 40, two FSH values above about 25 mIU/mL taken weeks apart raise concern for primary ovarian insufficiency and warrant clinician evaluation.
Low FSH with low estradiol points toward a hypothalamic or pituitary cause rather than ovarian aging.

Related symptom guides

Where to go next

Other by-age charts

Frequently asked questions

What is a normal FSH level by age?: In reproductive-age women FSH is roughly 3.5-12.5 mIU/mL in the follicular phase, with a mid-cycle surge up to about 21 mIU/mL. After menopause it rises to a representative range of about 25.8-134.8 mIU/mL. Ranges vary by laboratory.
What FSH level confirms menopause?: No single number confirms menopause. A sustained FSH above about 30 mIU/mL alongside 12 consecutive months without a period supports the diagnosis, but perimenopausal FSH fluctuates, so clinicians weigh symptoms and cycle history rather than one test.
Can FSH be high one month and normal the next?: Yes. During perimenopause FSH commonly swings between near-normal and clearly elevated from cycle to cycle. This day-to-day variability is exactly why a single FSH draw is unreliable for diagnosing the menopausal transition.
What does a low FSH level mean?: Low FSH, especially with low estradiol, suggests the signal from the hypothalamus or pituitary is reduced — seen in hypothalamic amenorrhea (from stress, low body weight, or overtraining) or pituitary conditions. A clinician evaluates the cause.

Primary medical sources

ClearHormones publishes editorial reference material for education only. Reference ranges vary between laboratories — always interpret your result with the clinician who ordered the test.